1. Technical Field
The present invention relates to deposition process equipment, and more particularly, to a susceptor for deposition process equipment, in which a resistance of an insulating ceramic material can be kept constant.
2. Related Art
Thanks to development of semiconductor and display device manufacturing technologies, various kinds of devices can be formed on a large substrate. Large substrates have at least 4-6 inch diameters. Uniform deposition of a thin film over the large substrate enables manufacture of superfine and superprecise devices. However, it is practically very difficult to deposit the thin film uniformly on the large substrate.
One type of device fabricated on large substrates is a liquid crystal display (LCD). The LCD includes an array substrate and a color filter substrate. A plurality of gate bus lines and a plurality of data bus lines perpendicularly crossing the plurality of gate bus lines are arranged to define a plurality of unit pixel regions on the array substrate. On each of the unit pixel regions, a pixel electrode made of a transparent metal, for example, indium tin oxide (ITO) and a thin film transistor (TFT) functioning as a switching device are formed. A plurality of R, G, and B color filters corresponding to the unit pixels are formed on the color filter substrate. The array substrate and the color filter substrate are attached to each other with a liquid crystal layer interposed therebetween. A metal layer, an insulating layer, an amorphous Si layer, and the like are sequentially formed on the transparent insulating substrate and etched through using 4-7 mask processes, thereby forming the gate bus lines, the data bus lines, a TFT channel layer, and source/drain electrodes.
Generally, plasma enhanced chemical vapor deposition (PECVD) is widely used to deposit a uniform thin film that forms the insulating layer during fabrication of semiconductor devices. Heating is desirable for stable growth of the deposition layer on the target substrate, such as glass or semiconductors. If the heating temperature is not optimized, the deposition layer grows unstably.
FIG. 1 is a plan view showing a susceptor coupled with a heater according to the related art. FIG. 2 is a sectional view showing a structure of a heater according to the related art.
Referring to FIGS. 1 and 2, a target substrate (not shown) is received on a susceptor provided in the PECVD or CVD equipment. The susceptor 100 includes a substrate 150 having a flat rectangular shape, a shaft (not shown) supporting the substrate 150, and heaters 110. Three or four heaters 110 are spaced apart by a predetermined interval from one another and are coupled to the susceptor 100 in a parallel direction with the substrate 150. Each of the heaters 110 includes a sheath 103 surrounding a heating wire 107 and input/output terminals 105 connected to the heating wire 107 to apply a current thereto.
Referring again to FIG. 2, the heater 110 includes the heating wire 107 generating heat, the input/output terminals 105 connected to both ends of the heating wire 107 to apply a current thereto, the sheath 103 surrounding the heating wire 107 with disposing a predetermined space therebetween, and an insulating ceramic material 108 filled in the predetermined space. That is, the input/output terminals 105 and the heating wire 107 connected to the input/output terminals 105 are provided in the interior of the sheath 103, and the predetermined space of the sheath 103 is filled with the insulating ceramic material 108. The insulating ceramic material 108 has a high resistance and high heat conductivity. Therefore, heat generated from the heating wire 107 is rapidly transferred to the sheath 103 and then the substrate 150 contacted with the sheath 103 is heated. MgO-based powder materials are generally used for the insulating ceramic material 108.
However, when the MgO-based insulating ceramic material 108 is used for the heaters 110 coupled to the susceptor 100, the insulating ceramic material 108 is exposed to ambient air at a top and a bottom of the sheath 103. The insulating ceramic material 108 absorbs moisture contained in the ambient air when contacting the ambient air. As the insulating ceramic material 108 absorbs the moisture, the resistance of the insulating ceramic material 108 decreases. Generally, a standard resistance range of the insulating ceramic material 108 is 2 MΩ to 20 MΩ. However, when the resistance decreases below the standard resistance range, the heating wire 107 breaks. The breakage of the heating wire 107 is one of the main reasons that the products resulting from the deposition contain defects. Further, the resistance drop of the insulating ceramic material 108 increases the current applied through the input/output terminals 105, thereby possibility causing a short-circuit between the heating wires 107 connected with the input/output terminals 105.